This is one of the most widely admired recordings of music of
this era; people from all backgrounds seem to enjoy it. The first
& last tracks are particularly impressive.

The polyphonic style of the era was to place a theme (chant, in
the case of liturgical settings) in the tenor (the lowest voice)
in long notes, and then to add "decoration" in the upper
voices. As such, the lines are not really independent, but are
dominated rhythmically by "cells" given by the notes of
the tenor. This is the typical organum. In the conductus (non-chant
based), the two main lines are sometimes more independent melodically,
but the rhythms are substantially similar. There is also a large
body of monophonic conducti (organa are polyphonic, by definition;
the monophonic version would be plainchant).